• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.637-642
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• 2008

The concept of district heating involves centralised heat production where heat is distributed to consumer via a piping network. The objective of this work is to identify the Flexible Pipe from an economy, execution, maintenance point of view. Flexible Pipe has in some countries, especially in Europe, been used for many years in district heating. In spite of years of experience, there still exist doubts about the possibilities of using flexible pipes in district heating applications, mostly because of no experiences in domestic market. The advantage of flexible pipe systems is their flexibility. This holds not only for the inner pipe but also for the total pipe system including insulation and jacket. Even for the largest diameter the minimum radius of curvature is given to 1.5m. The most important difference between flexible pipe systems and preinsulated steel pipes is their simple and quick assembly. Such information could provide a basis for making reasonable hypotheses about consumer preferences, to foam a basis for making future marketing more effective.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.825-828
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• 2005

Experimental and numerical study was done to confirm the effect of the flexible tube in pipeline on transient flow oscillation. Experiment was made for a pipeline with and without deformable flexible tube using a single pumping system of main stainless pipe. The wave speeds of main pipe and flexible tube were calculated from the pipe material properties, structures, and boundary conditions. Time dependent pressure fluctuations were calculated for the pipeline using the simple and the Kelvin-Voigt viscoelastic models for the deformation of main pipe and flexible tube. Pressure calculated by the Kelvin-Voigt viscoelastic model showed better agreement with measured one than pressure by the simple model. Experimental and numerical results show that the maximum pressure as well as amplitude of pressure oscillation was decreased by inserting short flexible tube in pipeline. Hence, inserted short flexible tube to pipeline was found to be effective for the suppression of strong pressure oscillation. Moreover, the wave speed in pipe was discussed based on numerical and experimental results.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.163-177
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• 2021

Numerical simulations of the Vortex-Induced Vibration (VIV) about a large-scale flexible pipe subject to shear flow were carried out in this paper. Efficiency verification was performed firstly, validating that the proposed fluid-structure interaction solution strategy is competent in predicting the VIV response. Then, the VIV characteristics related to multi-mode and spanwise hybrid waveform about the flexible pipe attributed to shear flow were investigated. When inflow velocity rises, higher vibration modes are apt to be excited, and the spanwise waveform easily convertes from a standing-wave-dominated status to a hybrid standing-traveling wave status. The multi-mode or even multiple-dominant-mode is prone to occur, that is, the dominant mode is often followed by several apparent subordinate modes with considerable vibration energy. Hence, the shedding frequencies no longer obey Strouhal law, and vibration trajectories become intricate. According to the motion analysis concerning the coupled cross-flow and in-line vibrations, as well as the corresponding wake patterns, a tight coupling interaction exists between the structural deformation and the wake flow behind the flexible pipe. In addition, the evolution of the vortex tube along the pipe span and a strong 3D effect are observed due to the slenderness of the flexible pipe and the variability of the vortex shedding attributed to the shear flow.

• 한국해양학회지:바다
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• 제13권3호
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• pp.237-245
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• 2008

우리는 해저 연약지반 주행차량과 주행차량의 상부에 결합되어 있는 유연관의 연성거동 동력학 해석 기법을 개발하였다. 연약지반 주행차량은 1개의 강체로 모델링되었으며, 질량집중매개변수 기법을 이용한 이산화기법을 적용하여 유연관을 모델링하였다. 강체 무한궤도 주행차량의 운동방정식과 유연관의 3차원 비선형 지배방정식을 결합시켰으며, 4개의 오일러 매개변수를 이용하여 주행차량과 유연관의 자세를 표현하였다. 주행차량과 유연관의 비선형 연성거동 동력학 방정식의 해를 구하기 위해, 증분-반복법을 이용하였다. 시간영역 수치적분을 위해 $Newmark-\beta$기법을 이용하였다. 증분-반복법을 적용하여 연성 운동방정식에 대한 자코비안 행렬을 유도하였다. 동적거동 동력학 해석 기법을 통해 유연관의 동적거동과 연약지반 위를 주행하는 무한궤도 차량의 동적거동 사이의 상호작용을 시간영역에서의 관찰하였다.

• 상하수도학회지
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• 제26권1호
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• pp.13-20
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• 2012

In this paper, we present the result of an investigation pertaining to the pipe stiffness of buried flexible pipes. Pipe stiffness (PS) formula for the parallel plate loading condition is derived based on the elasticity theory. Vertical and horizontal displacements are also derived. Vertical deflection is always larger than the horizontal deflection because some of energy due to overburden load is stored in the pipe but the difference is negligibly small. In the study, mechanical properties of the flexible pipes produced in the domestic manufacturer are tested and the results are reported in this paper. In addition, pipe stiffness is determined by the parallel plate loading tests and the finite element analysis. The difference between test and analysis is less than 14% although there are significant variations in the mechanical properties of the pipe material. Therefore, it was found that the finite element analysis can be used to predict the pipe stiffness instead of conducting parallel plate loading test.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.376-386
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• 2020

The aim of this study was to develop a new efficient strategy that uses the Vector form Intrinsic Finite-element (VFIFE) method to conduct the static and dynamic analyses of marine pipes. Nonlinear problems, such as large displacement, small strain, and contact and collision, can be analyzed using a unified calculation process in the VFIFE method according to the fundamental theories of point value description, path element, and reverse motion. This method enables analysis without the need to integrate the stiffness matrix of the structure, because only motion equations of particles established according to Newton's second law are required. These characteristics of the VFIFE facilitate the modeling and computation efficiencies in analyzing the nonlinear dynamic problem of flexible pipe with large deflections. In this study, a three-dimensional (3-D) dynamical model based on 3-D beam element was established according to the VFIFE method. The deep-sea flexible pipe was described by a set of spatial mass particles linked by 3-D beam element. The motion and configuration of the pipe are determined by these spatial particles. Based on this model, a simulation procedure to predict the 3-D dynamical behavior of flexible pipe was developed and verified. It was found that the spatial configuration and static internal force of the mining pipe can be obtained by calculating the stationary state of pipe motion. Using this simulation procedure, an analysis was conducted on the static and dynamic behaviors of the flexible mining pipe based on a 1000-m sea trial system. The results of the analysis proved that the VFIFE method can be efficiently applied to the static and dynamic analyses of marine pipes.

• 한국지반환경공학회 논문집
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• 제15권10호
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• pp.53-62
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• 2014

국내의 경우 하수관으로 많이 사용되어 온 관종은 콘크리트 흄관으로 대표되는 강성관이 주를 이루고 있으나, 시간 경과에 따른 관 부식 및 수밀성 부족 등의 이유로 사용이 급격히 감소하고 있다. 반면에 연성관은 부식에 강할 뿐만 아니라 자재의 무게가 경량이어서 시공성이 우수한 장점이 있어 사용이 증가하고 있는 실정이다. 그러나 연성관에 대한 시장의 신뢰성 부족과 미흡한 다짐관리로 인한 국부적인 파손사례가 발생하고 있어 이에 대한 원인분석 및 관리방안이 필요한 실정이다. 이에 본 연구에서는 시공순서, 관의 강성, 관 하부 콘크리트 기초의 강도, 관 하부 모래기초의 다짐도, 관 주변 모래의 다짐도 및 관 상단 되메움재의 다짐도 등을 변화시켜 가며 각각의 조건에 따른 관의 변형특성을 수치해석을 통하여 평가하였다. 평가결과 각 인자에 대한 영향을 확인할 수 있었으며 특히 연성관의 경우 관 주변 모래의 품질관리가 중요한 것으로 나타났다.

• 복합신소재구조학회 논문집
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• 제4권2호
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• pp.31-38
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• 2013

As the Sewer Pipe is transformed by the expansion of life cycle as a result of the technology development, flexible pipe is developed by the transformed environmental conditions. To change pipe design, three phases(compaction ration - inner deflection ratio - ring stiffness) should be considered in design conditions. The input data of pipe design were provided by compaction-inner deflection ratio-ring stiffness. M oreover, The guidelines of sewerage pipes should be considered by flexible pipes design criteria.

• Geomechanics and Engineering
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• 제3권3호
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• pp.169-188
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• 2011

Response of buried flexible pipe-soil system is studied, through numerical analysis, with respect to deflection and buckling in a spatially varying soil media. In numerical modeling procedure, soil parameters are modeled as two-dimensional non-Gaussian homogeneous random field using Cholesky decomposition technique. Numerical analysis is performed using random field theory combined with finite difference numerical code FLAC 5.0 (2D). Monte Carlo simulations are performed to obtain the statistics, i.e., mean and variance of deflection and circumferential (buckling) stresses of buried flexible pipe-soil system in a spatially varying soil media. Results are compared and discussed in the light of available analytical solutions as well as conventional numerical procedures in which soil parameters are considered as uniformly constant. The statistical information obtained from Monte Carlo simulations is further utilized for the reliability analysis of buried flexible pipe-soil system with respect to deflection and buckling. The results of the reliability analysis clearly demonstrate the influence of extent of variation and spatial correlation structure of soil parameters on the performance assessment of buried flexible pipe-soil systems, which is not well captured in conventional procedures.

• 상하수도학회지
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• 제31권1호
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• pp.7-12
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• 2017

Most of existing buried pipes are composed of reinforced concrete. Reinforced concrete pipes have many problems such as aging, corrosion, leaking, etc. The polyethylene (PE) pipes have advantages to solve these problems. The plastic pipes buried underground are classified into a flexible pipe. National standard that has limited the long-term vertical deformation of the pipe to 5% for flexible pipes including PE pipe. This study presents a prediction for the long-term behavior of the polyethylene pipe based on ASTM D 5365. This prediction method is presented to estimate by using the statistical method from the initial deflection measurement data. We predict the behavior of long-term performance on the double-wall pipe and multi-wall pipe. As a result, it was found that the PE pipe will be sound enough more than 50 years if the compaction of soil around the pipe is more than 95% of the standard soil compaction density.